Exemplary embodiments relate to a nonvolatile memory device.
A nonvolatile memory device has the advantages of random access memory (RAM), such as enabling the writing and erasure of data, and read only memory (ROM), such as retaining data even without the supply of power, and so has recently been widely used for the storage media of portable electronic devices, such as digital cameras, personal digital assistants (PDAs), and MP3 players.
The memory cells of a nonvolatile memory device may be coupled to word lines WL and bit lines BL. A memory cell coupled to a selected word line and a selected bit line may be selected, and data may be programmed into the selected memory cell or data stored in the selected memory cell may be read.
In general, a program operation is performed on the nonvolatile memory device by supplying a program voltage to a word line of a plurality of word lines, selected for a program, and supplying a pass voltage to the remaining unselected word lines.
To supply the program voltage or the pass voltage to each of the word lines, the corresponding word line may be coupled to a global word line GWL through which the voltage is supplied. Each of the global word lines GWL may be coupled to a voltage supply unit, which supplies the necessary voltage.
Furthermore, the voltages supplied to the global word lines GWL may be determined in response to a control signal inputted to a control unit for controlling the operations of the nonvolatile memory device. That is, a program voltage may be supplied to a global word line GWL coupled to a word line selected for a program, and a pass voltage may be supplied to global word lines GWL coupled to the remaining word lines. To this end, the control unit may control the voltage supply unit so that it generates a variety of voltages, supplies the variety of voltages to the respective global word lines GWL, and also selects and outputs a voltage required by each of the global word lines GWL.
Meanwhile, in the program operation of the nonvolatile memory device, a local self-boosting method of supplying several levels of voltage may be used so that the threshold voltages of peripheral memory cells, which are not selected to be programmed, are not changed.
Accordingly, various kinds of voltages may be supplied to the global word lines GWL for supplying the operating voltages to the word lines WL, and therefore, the number of control signals that should be output by the control unit in order to set up the kinds of voltages for the respective global word lines GWL may be great. Accordingly, the number of control lines for supplying the control signals may be great.
The number of control lines t necessary to control the voltage is shown in the following equation 1.t=Number of planes×Number of word lines×Number of voltage levels  [Equation 1]
For example, it is assumed that a nonvolatile memory device includes two planes, each of the planes includes a plurality of memory blocks, each of the memory blocks includes 32 word lines, and the number of voltage levels of an operating voltage for a program, read, or erase operation is 5. In this case, t=2×32×5=320.
According to Equation 1, the number of control lines t is the number of planes×the number of word lines×the number of voltage levels. Therefore, a small increase in either the number of word lines, the number of voltage levels, or the number of planes, may result in a relatively large increase in the number of control lines. For example, if the number of word lines is increased in order to increase the capacity of a nonvolatile memory device and the number of voltage levels of operating voltages is increased in order to improve the operation, the number of control lines is also increased. And if the number of control lines is increased, the area occupied by the control lines in the layout of the nonvolatile memory device is also increased.